各向异性叠前时间偏移--以东濮凹陷为例

A new method of anisotropy pre-stack time migration

建立精准的偏移速度场是复杂地质构造成像的核心.常规的速度分析方法在大炮检距、地层界面倾斜或弯曲、盐下及深部多层介质等情况下精度不高,影响到地震成像效果与解释结果的可靠性.为解决这个问题,采用了一套叠前时间偏移速度场建立的新方法:初始偏移速度求取和双谱法高密度逐点速度分析,即通过合理的参数提取和速度计算,提高动校正精度,基本消除各向异性影响.把获得的速度和各向异性参数作为Kirchhoff叠前时间偏移的基本参数进行叠前时间偏移处理,从而提高叠前偏移成像精度.通过在东濮凹陷BM和MC地区的实际应用取得了较好的效果.

Imaging of complicated geological structure is one of the major difficulties in the field of seismic exploration, and the main factor of imaging is migration of the velocity field. Therefore, constructing accurately the migration velocity field is not only the core of high precision imaging, but also the nexus between seismology and geology. In fact, the accuracy of velocity that is picked with the conventional method is rather low under the large offsets, dipping or bend interfaces, pre-salt and deep multilayered medium. As a result, it reduces the accuracy of seismic imaging as well as the reliability of imaging and interpretation. To solve this problem, a new method of PSTM velocity field building is adopted, that is, initial velocity of migration acquiring, bi-spectral high density velocity analysis and anisotropy PSTM. The practical result has proved its good effect and the real accuracy of migration has been increased much.